An array CSMT exploration technology is to be newly developed in order to accurately explore the fault group which relates to the geothermal reservoir. The array CSMT is an MT with an artificial signal source as well as stations laid in array along the traverse line. The result in fiscal 1992 was reported. Measurement was made possible by automatically switching the frequency as per the time schedule fixed in advance with a transmitter/receiver in the unit which was built in fiscal 1991 and presently modified. Software improvement was also made in the processing of two-dimensional inversion analysis data by the present method jointly with the MT. Notwithstanding an area which was comparatively high in noise level, good data were acquired through an application test in the Sengan area where the existence of geothermal reservoirs was confirmed. That area was known to be structured of three strata, i.e., high-resistivity stratum on the shallow subsurface, remarkably low-resistivity one on the medium subsurface and medium-resistivity one on the deep subsurface. Several low-resistivity zones were detected which indicated the geothermal alternation, and fairly reflected the fracture system structure and altered zone. 13 refs., 32 figs., 7 tabs.